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Biomedical subjects

Mark H Kaplan

Publications and source records attributed to Mark H Kaplan.

At least 19 recordsLinked to original sources

Guidelines for T cell nomenclature.

Advances in T cell biology have revealed heterogeneity among T cell populations that is not captured by existing general nomenclature. This issue has caused an ad hoc broadening of core T cell subset definitions and the invention of new subset designations that have not been uniformly delineated. To address this issue, in this Consensus Statement, we propose guidelines that serve three goals. First, they advocate that primary research reports define the experimental basis by which relevant subsets are designated in the methods section of each study. Second, they provide standardized definitions for existing subset designations in popular use, and common experimental criteria for defining each subset are noted. Last, they present an alternative 'modular nomenclature' paradigm. The newly proposed modular nomenclature eschews conceptualization of antigen-experienced T cells as belonging to a few idealized subsets, and the nomenclature instead simply indicates individual biological properties present in a T cell population with brief descriptors. Collectively, these guidelines intend to enhance transparency in the literature while facilitating clearer communication of findings and concepts to researchers, students and clinicians.

Terminology as Topic↗

Bruton's tyrosine kinase is required for TLR-induced IL-10 production.

Bruton's tyrosine kinase (Btk) is a critical signaling mediator downstream of the B cell Ag receptor. X-linked agammaglobulinemia is caused by mutations in Btk resulting in multiple defects in B cell development and function, and recurrent bacterial infections. Recent evidence has also supported a role for Btk in TLR signaling. We demonstrate that Btk is activated by TLR4 in primary macrophages and is required for normal TLR-induced IL-10 production in multiple macrophage populations. Btk-deficient bone marrow-derived macrophages secrete decreased levels of IL-10 in response to multiple TLR ligands, compared with wild-type (WT) cells. Similarly, Btk-deficient peritoneal and splenic macrophages secrete decreased IL-10 levels compared with WT cultures. This phenotype correlates with Btk-dependent induction of NF-kappaB and AP-1 DNA binding activity, and altered commensal bacteria populations. Decreased IL-10 production may be responsible for increased IL-6 because blocking IL-10 in WT cultures increased IL-6 production, and supplementation of IL-10 to Btk-deficient cultures decreased IL-6 production. Similarly, injection of IL-10 in vivo with LPS decreases the elevated IL-6 serum levels during endotoxemia in Btk-deficient mice. These data further support a role for Btk in regulating TLR-induced cytokine production from APCs and provide downstream targets for analysis of Btk function.

Agammaglobulinaemia Tyrosine Kinase↗

T-bet is a critical determinant in the instability of the IL-17-secreting T-helper phenotype.

IL-23, an IL-12-related cytokine, induces an IL-17-secreting T-helper phenotype that is involved in autoimmune diseases and host defense against certain pathogens. Although the transcription factors required for development of IL-23-stimulated cells are unknown, we show that T-bet is a critical negative regulator of the IL-23-primed T-cell phenotype, which we term Th1beta. Th1 or Th1beta Tbx21-/- cultures secrete higher than WT levels of IL-17 in response to T-cell receptor (TCR) or IL-23 + IL-18 stimulation. Ectopic T-bet expression in Th1beta cells promotes IFN-gamma secretion but decreases IL-17 production. Although antigen-receptor stimulation of Th1beta cells stimulates IL-17 production, it also induces the IFN-gamma-independent expression of T-bet and progression to a Th1 cytokine secretion pattern. T-bet is required for the progression to the Th1 phenotype, because Tbx21-/- Th1beta cultures maintain the IL-17-secreting phenotype after 2 weeks of culture. Addition of IFN-gamma to Tbx21-/- Th1beta cultures cannot recover the progression to the Th1 phenotype, suggesting T-bet, rather than IFN-gamma, mediates Th1beta to Th1 progression. The transient nature of the Th1beta phenotype suggests that these cells are a component of type I immunity and that T-bet expression is a critical determinant of Th1 versus Th1beta cell fate.

Animals↗

p53 regulates Btk-dependent B cell proliferation but not differentiation.

Btk is critical for B cell development and proliferation. Mice lacking Btk have a defect in B cell development, resulting in a loss of mature B cells and decreased proliferative responses following B cell receptor cross-linking. In contrast, mice deficient in the tumor suppressor p53 display increases in developing B cell populations in the bone marrow. To investigate the potential role of p53 in Btk-dependent B cell development and function, we generated mice doubly-deficient in p53 and Btk. Btk/p53-deficient mice showed an increase in splenic B220+ cell numbers compared with Btk-deficient mice, although there was no recovery in B cell subset differentiation. In contrast to the lack of recovery of B cell development, there was a recovery in lipopolysaccharide and anti-immunoglobulin M (IgM) plus interleukin-4-induced proliferation of Btk/p53-deficient B cells, although there was no recovery to anti-IgM stimulation alone. Thus, p53 promotes B cell expansion and proliferation, but p53 deficiency cannot compensate for Btk deficiency in the development of B cell subsets.

Agammaglobulinaemia Tyrosine Kinase↗

Tobacco and HIV.

The risks to an HIV-infected person who smokes are dramatically amplified compared with the general population. Smoking has been shown to be an independent risk factor for non-AIDS-related mortality in patients who have HIV, even in patients who receive highly active antiretroviral therapy. It has been independently associated with lower scores for quality-of-life indices, such as general health perception, physical functioning, bodily pain, energy, and cognitive functioning. Over time, considering the significant pathology elicited by tobacco, it is hoped that smoking cessation will help reduce the risks of lung disease, heart disease, and neoplastic conditions in patients who have HIV and increase their general sense of well-being.

HIV Infections↗

Detection of HERV-K(HML-2) viral RNA in plasma of HIV type 1-infected individuals.

Approximately 8% of the human genome sequence is composed by human endogenous retroviruses (HERVs), most of which are defective. HERV-K(HML-2) is the youngest and most active family and has maintained some proviruses with intact open reading frames (ORFs) that code for viral proteins that may assemble into viral particles. Many HERV-K(HML-2) sequences are polymorphic in humans (present in some individuals but not in others) and probably many others may be unfixed (not inserted permanently in a specific chromosomal location of the human genome). In the present study HIV-1 and HCV-1-positive plasma samples were screened for the presence of HERV-K(HML-2) RNA in an RT-PCR using HERV-K pol specific primers. HERV-K(HML-2) viral RNA sequences were found almost universally in HIV-1(+) plasma samples (95.33%) but were rarely detected in HCV-1 patients (5.2%) or control subjects (7.69%). Other HERV-K(HML-2) viral segments of the RNA genome including gag, prt, and both env regions, surface (su), and transmembrane (tm) were amplified from HERV-K pol-positive plasma of HIV-1 patients. Type 1 and type 2 HERV-K(HML- 2) viral RNA genomes were found to coexist in the same plasma of HIV-1 patients. These results suggest the HERV-K(HML-2) viral particles are induced in HIV-1-infected individuals.

Endogenous Retroviruses↗

Influence of increased CD4 cell counts on the genetic variability of hepatitis C virus in patients co-infected with human immunodeficiency virus I.

In order to study the effect of increased CD4 cell counts on the biology of hepatitis C virus (HCV), we analyzed the genetic variability of HCV generated over 8 y in eight human immunodeficiency virus-1 (HIV-1) and HCV co-infected patients. This was a retrospective study in which HIV patients were selected who had profound immune impairment evident over four years and were co-infected with HCV genotype 1 and who then went on highly active antiretroviral therapy (HAART). These patients achieved different degrees of immune reconstitution, measured as increased CD4 cell counts during a 4- to 8-y period, following initiation of HAART. HCV genetic variability was determined by measuring the genetic diversity (Hamming distance, HD), and complexity (number of viral variants) in plasma samples collected at yearly intervals just before and after the initiation of HAART. The parameters were assessed by molecular cloning and sequencing of a 575-bp fragment including the HCV envelope 1 and envelope 2 genes (E1/E2), containing the hypervariable region 1 (HVR1). significantly increased HVR1 genetic diversity was observed in analyzed samples where the patients' CD4 cell counts were > or =100 compared with CD4 cell counts <100. A significant increase in genetic diversity in HVR1 was detected in co-infected patients whose CD4 cell counts increased from <100 to >400 over a period of more than 4 y of HAART therapy. This was in contrast to a minimal increase in HCV genetic diversity of HVR1 occurring in patients whose CD4 cell counts failed to rise much over 200 over 7 y of follow up. Insertion and deletion of HCV genomic fragments in the E1/E2 region was documented in one patient who developed fulminant hepatitis C.

Amino Acid Sequence↗

Epigenetic regulation of WTH3 in primary and cultured drug-resistant breast cancer cells.

Previous studies showed that the WTH3 gene functioned as a negative regulator during multidrug resistance (MDR) development in vitro. To understand whether this gene is also involved in clinical drug resistance, hypermethylation at its promoter region observed in cultured MDR MCF7/AdrR cells was examined in primary drug-resistant breast cancer epithelial cells isolated from effusions of breast cancer patients. The results showed that this event also occurred in drug-resistant breast cancer epithelial cells and a newly induced drug-resistant cell line, MCF7/inR. Interestingly, we found that a CpG (CpG 23) that was close to the TATA-like box was constantly methylated in the WTH3 promoter of drug-resistant breast cancer epithelial and cultured MDR cells. Mutagenic study suggested that this CpG site had a functional effect on promoter activity. We also discovered that MCF7/AdrR cells treated with trichostatin A, a histone deacetylase inhibitor, exhibited higher WTH3, but lower MDR1, expression. A reverse correlation between WTH3 and MDR1 gene expression was also observed in MCF7/AdrR, and its non-MDR parental cell line, MCF7/WT. This result indicated that both DNA methylation and histone deacetylase could act in concert to inhibit WTH3 and consequently stimulate MDR1 expression. This hypothesis was supported by data obtained from introducing the WTH3 transgene into MDR cell lines, which reduced endogenous MDR1 expression. Therefore, our studies suggested that the behavior of WTH3 in primary drug-resistant breast cancer epithelial cells was similar to that in a model system where epigenetic regulation of the WTH3 gene was linked to the MDR phenotype.

Base Sequence↗

The role of constitutively active Stat6 in leukemia and lymphoma.

Signal transducers and activators of transcription (STAT) are a family of transcription factors that regulate a broad range of cellular processes, such as proliferation, differentiation, and survival, in a large variety of cell types. Because of their regulation of diverse cellular functions, their aberrant activation is frequently associated with disease development, particularly oncogenic diseases. Much evidence exists to suggest that STAT proteins play a significant role in cellular transformation. However, which STAT proteins and to what extent they cause transformation and subsequent disease progression are topics currently being investigated. In this review, we will report on the findings concerning the involvement of Stat6 in the development of lymphoma and leukemia. Mounting evidence, in both patients and mouse models, supports a model where Stat6 is not a mere bystander, but rather, plays an active role in promoting a transformed phenotype.

Animals↗

Differential requirement of signal transducer and activator of transcription-4 (Stat4) and Stat6 in a thyrotropin receptor-289-adenovirus-induced model of Graves' hyperthyroidism.

T helper type 1 (Th1) and Th2 cells have critical roles in the development of cell-mediated and humoral immune responses, respectively. This division of function predicts that Th1 cells mediate inflammatory diseases and Th2 cells promote antibody (Ab)-mediated autoimmunity. Our previous studies using HEK-293 cells expressing the extracellular domain of the TSH receptor (TSHR) showed that Stat4-/- mice, which lack Th1 cells, are susceptible, whereas Stat6-/- mice, which lack Th2 cells, are resistant to the induction of Graves' hyperthyroidism. To investigate the role of Stat4 and Stat6 genes in other murine models of hyperthyroidism, we injected wild-type BALB/c, Stat4-/-, and Stat6-/- mice with an adenovirus expressing amino acid residues 1-289 of TSHR (TSHR-289-ad or 289-ad). The viral system induces a much stronger immune response with much more rapid onset of disease. Our results showed that 56% of wild-type, 75% of Stat4-/-, and 39% of Stat6-/- mice developed hyperthyroidism. Hyperthyroid mice exhibited thyroid stimulatory Abs. The Stat4-/- mice developed a higher incidence and greater severity of hyperthyroidism compared with wild-type and Stat6-/- mice. BALB/c and Stat4-/- mice showed significantly higher TSHR Abs of the IgG1 subclass and IL-4 compared with Stat6-/- mice. In contrast, Stat6-/- mice had predominantly the IgG2a subclass of TSHR Ab and produced significantly higher amounts of IFN-gamma than BALB/c and Stat4-/- mice. All hyperthyroid mice showed enlarged thyroid glands with hyperactivity. These results suggest that in the TSHR-289-ad model, the Th2 cells are more efficient in mediating disease, but in the absence of Th2 cells, Th1 cells may still initiate a reduced incidence of Graves' hyperthyroidism.

Adenoviridae↗

Interleukin (IL)-4 inhibits IL-10 to promote IL-12 production by dendritic cells.

Interleukin (IL)-4 is known to be the most potent cytokine that can initiate Th2 cell differentiation. Paradoxically, IL-4 instructs dendritic cells (DCs) to promote Th1 cell differentiation. We investigated the mechanisms by which IL-4 directs CD4 T cells toward the Th1 cell lineage. Our study demonstrates that the IL-4-mediated induction of Th1 cell differentiation requires IL-10 production by DCs. IL-4 treatment of DCs in the presence of lipopolysaccharide or CpG resulted in decreased production of IL-10, which was accompanied by enhanced IL-12 production. In IL-10-deficient DCs, the level of IL-12 was greatly elevated and, more importantly, the ability of IL-4 to up-regulate IL-12 was abrogated. Interestingly, IL-4 inhibited IL-10 production by DCs but not by B cells. The down-regulation of IL-10 gene expression by IL-4 depended on Stat6 and was at least partly caused by decreased histone acetylation of the IL-10 promoter. These data indicate that IL-4 plays a key role in inducing Th1 cell differentiation by instructing DCs to produce less IL-10.

Acetylation↗

Impaired interferon-gamma production as a consequence of STAT4 deficiency after autologous hematopoietic stem cell transplantation for lymphoma.

Production of interferon gamma (IFN-gamma) is critical for optimal antitumor immunotherapy in several preclinical animal models. Interleukin-12 (IL-12)-induced IFN-gamma production is markedly defective after autologous stem cell transplantation. Quantitative deficiency in CD4 T cells, relative increase in CD25+CD4+ T cells, and bias toward T helper 2 (Th2) differentiation are not the primary mechanisms of defective IFN-gamma production. IL-12 receptor beta1 (IL-12Rbeta1) and IL-12Rbeta2 are expressed at equivalent or higher levels on posttransplantation patient peripheral blood mononuclear cells (PBMCs) as compared with control PBMCs. IL-12-induced tyrosine phosphorylation of signal transducer and activator of transcription 4 (STAT4) was undetectable or barely detectable in posttransplantation patient PBMCs, whereas IL-4-induced tyrosine phosphorylation of STAT6 did not differ in posttransplantation patient and control PBMCs. Levels of STAT4 protein were decreased by 97% in posttransplantation patient PBMCs. Levels of STAT4 mRNA were also significantly decreased in posttransplantation patient PBMCs. Incubation with IL-12 and IL-18 in combination partially reversed the defective IFN-gamma production by posttransplantation patient PBMCs. IFN-gamma production in response to IL-12 plus IL-18 did not require increased expression of STAT4 but was dependent on the activity of p38 mitogen-activated protein kinase (MAPK). These results indicate that defective IFN-gamma production is due to an intrinsic deficiency in STAT4 expression by posttransplantation patient lymphocytes and suggest strategies for circumventing this deficiency in cancer immunotherapy.

Case-Control Studies↗

Constitutive expression of CIITA directs CD4 T cells to produce Th2 cytokines in the thymus.

We generated mice expressing a human type III CIITA transgene (CIITA Tg) under control of the CD4 promoter to study the role of CIITA in CD4 T cell biology. The transgene is expressed in peripheral CD4 and CD8 T cells, as well as in thymocytes. When CD4 T cells were differentiated towards the Th2 lineage, both control and CIITA Tg Th2 cells expressed similar levels of Th2 cytokines. Th1 cells from control and CIITA Tg mice cells produced comparable levels of IFN-gamma. CIITA Tg Th1 cells also expressed IL-4, IL-5, and IL-13 in the absence of Stat6. There was an approximate 10-fold increase in the number of peripheral naïve CD4 T cells and NK1.1- thymocytes producing IL-4 from CIITA Tg mice compared to control mice. Finally, Th1 cells from irradiated control mice reconstituted with CIITA Tg bone marrow displayed the same cytokine production profiles as Th1 cells from CIITA Tg mice. Together, our data demonstrate that CIITA expression pre-disposes CD4 T cells to produce Th2 type cytokines. Moreover, phenotypic similarities between Th1 cells expressing the CIITA transgene and CIITA deficient Th1 cells suggest that the role of CIITA in cytokine regulation is complex and may reflect both direct and indirect mechanisms of T cell development and differentiation.

Adoptive Transfer↗

PU.1 expression delineates heterogeneity in primary Th2 cells.

Primary T helper 2 cells are heterogeneous, expressing subsets of cytokines at varying levels. Mechanisms controlling this spectrum of phenotypes are still unclear. The ETS family transcription factor PU.1 is expressed in Th2 but not Th1 cells. Th2 cytokine production is decreased in cultures transduced with a PU.1-expressing retrovirus and increased in Th2 cells following RNAi that decreases PU.1 expression. In primary cultures, PU.1 expression is restricted to a subpopulation of Th2 cells that express CCL22 and a subset of Th2 cytokines. PU.1 regulates the Th2 phenotype by interfering with GATA-3 DNA binding without altering GATA-3 protein levels. Thus, the expression of PU.1 in subsets of Th2 cells establishes a defined cytokine profile and contributes towards establishing the spectrum of cytokine production observed in Th2 populations.

Animals↗

STAT4: a critical regulator of inflammation in vivo.

Signal transducer and activator of transcription 4 (STAT4) is a central mediator in generating inflammation during protective immune responses and immune-mediated diseases. In the 8 yr since their first description, STAT4-deficient mice have defined the role of STAT4 in a variety of in vivo model systems. Despite the extensive study and use of these mice, the exact role of STAT4 in vivo is still unclear. In this review, I focus on describing the phenotypes of STAT4-deficient immune responses to pathogens and in diseases. Comparing the effects of STAT4 deficiency among numerous model systems will further enhance the development of a systemic model of STAT4 function in vivo.

Animals↗

Altered Th1 cell differentiation programming by CIITA deficiency.

CD4 T cell differentiation is a complex process affected by many transcription factors interacting in a tightly regulated manner. We have previously shown that CIITA-deficient mouse Th1 cells expressed Th2-type cytokines, while IFN-gamma expression was normal. In this study, we show that CIITA-deficient Th1 cells contain three distinct populations: cells secreting IL-4 alone, IFN-gamma alone, and both IL-4 and IFN-gamma together. This novel phenotype is stable over multiple rounds of stimulation in the presence of Th1-inducing factors. CIITA-deficient Th1 cells require TCR-mediated signaling to express Th2 cytokines, and this occurs with similar kinetics as wild-type Th2 cells. Both GATA-3 and IL-4 appear to be required for CIITA-deficient Th1 cells to express Th2-type cytokines. Interestingly, however, CIITA-deficient Th1 cells can produce IL-4 in the absence of exogenous IL-4. Introducing either CIITA or antisense GATA-3 during Th1 differentiation partially reduces Th2-type cytokine expression. With the exception of Th2-type cytokine expression, Th1 differentiation occurs normally in the absence of CIITA, as measured by expression of T-bet, IL-12Rbeta2, IL-18Ralpha, and IFN-gamma. Therefore, CIITA plays a key role to repress Th2-type cytokine expression as naive CD4 T cells differentiate toward the Th1 lineage.

Animals↗

Cutting edge: induction of the antigen-processing enzyme IFN-gamma-inducible lysosomal thiol reductase in melanoma cells Is STAT1-dependent but CIITA-independent.

Presentation and CD4(+) T cell responses to Ag in the context of MHC class II molecules require processing of native proteins into short peptide fragments. Within this pathway, IFN-gamma-inducible lysosomal thiol reductase (GILT) functions to catalyze thiol bond reduction, thus unfolding native protein Ag and facilitating further processing via cellular proteases. In contrast with professional APCs such as B cells, class II-positive human melanomas expressed relatively little to no GILT protein or mRNA. Tumor cell GILT expression was partially restored with IFN-gamma treatment but unlike other genes required for class II Ag presentation, GILT was not regulated by CIITA. Rather, studies revealed STAT1 plays a direct role in IFN-gamma-inducible GILT expression. These results define a molecular mechanism for the uncoupled regulation of MHC class II genes and the processing enzyme GILT in human melanomas.

Antigen Presentation↗

Signal transducer and activator of transcription (Stat)-6-dependent, but not Stat4-dependent, immunity is required for the development of autoimmunity in Graves' hyperthyroidism.

The role of T helper (Th) cells in experimental models of Graves' hyperthyroidism is still somewhat controversial. To further investigate the role of Th1- and Th2-dependent immunity during the development of Graves' hyperthyroidism, we tested mice with targeted deletion of signal transducer and activator of transcription-4 (Stat4) or Stat6 genes that, respectively, have impaired Th1 and Th2 immunity. We immunized wild-type BALB/c, Stat4(-/-), or Stat6(-/-) mice with human embryonic kidney cells (293 cells) expressing the extracellular domain of human TSH receptor (293-TBP cells). Fifty percent of wild-type BALB/c and Stat4(-/-) mice developed Graves' hyperthyroidism with elevated serum T(4) levels and thyroid stimulatory antibodies. In contrast, Stat6(-/-) mice resisted development of the disease. Stat4(-/-) mice exhibited a dominant Th2 immune response characterized by the production of IL-4 and IgG1 anti-TSH receptor antibodies. However, Stat6(-/-) mice displayed a strong Th1 immune response characterized by the production of interferon-gamma and IgG2a antibodies. Hyperthyroid mice showed enlargement of thyroid glands with hypertrophy and decreased amounts of colloid material, all characteristics of Graves' disease. These data demonstrate that in this model, Stat6-dependent Th2 immunity is critical for the development of Graves' hyperthyroidism.

Animals↗